1. Field of the Invention
This invention relates to electrophotographic photosensitive members and more particularly to an electrophotographic photosensitive member containing a specific disazo pigment.
2. Description of the Prior Art
Photosensitive members containing an inorganic photoconductive material such as selenium, cadmium, sulfide, or zinc oxide have so far been widely used for electrophotography.
On the other hand, various organic photoconductive materials for use in electrophotographic photosensitive members are known including typical photoconductive polymer poly(N-vinylcarbazole), low molecular weight organic photoconductive materials such as 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, and further combinations of such organic photoconductive material with various kinds of dyes or pigments.
Since an electrophotographic photosensitive material comprising an organic photoconductive material is excellent in film-forming capability and is produced by coating, the organic electrophotographic photosensitive member can be produced with high productivity and inexpensively. Color sensitivity of the photosensitive members can be freely controlled by selecting dyes or pigments to be used. Having such advantages, photosensitive members of various organic photoconductive materials have been investigated extensively. Known pigments for this purpose include disazo pigments, for example, disclosed in U.S. Pat. No. 4,251,613 (Japanese Patent Kokai No. 12742/1979) and Japanese Patent Kokai Nos. 145142/1979 and 82160/1980. However, photosensitive members employing the known pigments are disadvantageous in sensitivity and durability, so that very few of them have been put into practical use.